1. Field
Aspects of the present teachings relate to multi-filter chemical speciation samplers to collect particulate matter (PM) fractions from ambient air, and virtual impaction particle separation inlets for the same.
2. Description of the Related Art
Airborne particulate matter (PM) is one of the major components of air pollution. PM includes microscopic particles in the air that are generally classified by size as being coarse PM or fine PM. The fine PM includes particles having an aerodynamic diameter (AD) of less than 2.5 microns (μm), and the coarse PM includes particles having an AD of between 2.5 and 10 μm.
PM can be released directly to the atmosphere from natural and anthropogenic sources, such as, industrial smokestacks, automobile tailpipes, wood burning, road dust, wind blown dust, and biological materials (spores and pollen), for example. PM can also form in the atmosphere from chemical reactions involving other pollutants, such as sulphur dioxide (SO2), nitrogen oxides (NOx), ammonia (NH3), and volatile organic compounds (VOC).
Large particles (>10 μm AD) are generally filtered out by the nose. Middle-size or coarse particles (2.5 μm to 10 μm AD) are deposited in the upper airways, where they can impact on surfaces in the throat, larynx and upper branches of the lungs. Coarse PM may consist of several potentially toxic components, such as resuspended particulate matter from paved and unpaved roads, industrial materials, brake linings, tire residues, trace metals, and bio-aerosols. A considerable portion of these particles may be deposited in the upper airways and to a lesser extent into the lower airways, and may be responsible for the exacerbation of asthma and other respiratory disease. Recent data from a small number of epidemiological studies indicate that, apart from, or in addition to, the fine PM, health effects may also be closely associated with the coarse PM, to an even larger extent than to the fine PM. In vitro studies with human monocytes have shown that cellular toxicity and inflammation may also be associated with the coarse PM and its biological components.
In addition, fine PM reaches the alveoli, where it must be dealt with by macrophages from the immune system. Fine PM can be inhaled deep into the lungs and reach the critical areas where the cells replenish the blood with oxygen. They can cause breathing and respiratory symptoms, irritation, inflammation and damage to the lungs. Health studies have shown significant associations between exposure to fine PM and premature death from heart or lung disease. Fine PM also aggravates heart and lung diseases and has been linked to effects, such as cardiovascular symptoms, cardiac arrhythmias, congestive heart failure, heart attacks, respiratory symptoms, asthma attacks, and bronchitis. These effects can result in increased hospital admissions, emergency room visits, absences from school or work, and restricted activity days. Individuals that may be particularly sensitive to fine PM exposure include people with heart or lung disease, older adults, and children.
Accordingly, the U.S. Environmental Protection Agency (EPA) has published rules setting forth air quality designations and classifications for fine PM, pursuant to the National Ambient Air Quality Standards (NAAQS). The U.S. EPA has recently considered (2006) rules for coarse PM but at that time the lack of evidence associating coarse particles to health effects was lacking. The U.S. EPA will likely consider a PMc standard in the next round of NAAQS. To support this effort and learn more about PMc and health effects, the U.S. EPA is developing a coarse particle chemical speciation network, where the material collected on filters will be analyzed in the laboratory for different chemical components. Despite the growing evidence of particulate-related health effects, the paucity of information about specific biological mechanisms, associated with both fine and coarse particles, remains a critical missing link.
Accordingly, a need exists for size-fractionating PM from ambient air, separating the fractionated PM into coarse and fine fractions, and then further separating the coarse fraction into coarse aliquots collected on separate filters, which can be separately analyzed.